This invention relates to apparatus for the production of tagged packets, such as infusion bags, in which a tag and thread length is attached to the bag envelope of filter material to allow the bag to be suspended from the tag in use.
When producing such tagged packets it is generally undesirable to allow the tag to hang free from the bag by its thread because when a number of such packets are packaged together the threads can easily become entangled. Generally, therefore, the tag is temporarily attached to the bag in addition to securing the end of the thread remote from the tag permanently to the bag.
A simple way of placing the thread is lay it across the filter material while it is still a flat web, attaching the tag near one side edge and securing the opposite end of the thread near the other side edge. In this arrangement, however, the width of the web determines the length of the thread and that length may be undesirably limited. In order to provide an ample length of thread it is known to give the thread a convoluted pattern on the web, but the mechanisms to produce such patterns are relatively complicated.
It is also known to increase the length of the thread by drawing a tag attached to one end of the thread across the web to an extended position beyond the side edge of the web, thus returning to tag to a final position over the web near that side edge to attach it to the web. Although the additional length is obtained by a simple rectilinear movement, if it is required to attach the tag to the web on or near the line of the thread, it is necessary to ensure that the tag drawing means does not clash with the tag-web attaching means.
According to one aspect of the present invention, apparatus is provided for attaching a tag and length of thread length to a web of filter material, one end of the thread being secured to the tag and the other end being secured to the web adjacent one side edge, and the tag being attached to the web adjacent the opposite side edge, the apparatus comprising gripper means for drawing the tag beyond said opposite side edge before returning the tag to a final extended position over the web, and means for attachment of the tag to the web in said final position, a displacement mechanism for said gripper means comprising a first linear guide on which the gripper means is slidable, and a second linear guide transverse to said first guide on which said first guide is slidable, said second guide being fixedly located in the apparatus, whereby the gripper means is movable in the mutually transverse directions of the guides, both transversely across the web to said extended and final positions and longitudinally of the web away from the tag-attaching means.
In this manner a relatively simple and robust mechanism can be provided that will lay the extended length of thread across the web and also begin the return movement of the gripper means past the tag-attaching means by guiding the gripper means longitudinally of the web to clear the attaching means.
Preferably, said first linear guide extends transversely across the web and said second linear guide on which the first guide is slidable extends longitudinally of the web.
The use of the form-fill process for producing filled packets is well known, the packet filter material in the form of a continuous web being shaped into a tube around a forming tube through which the filling material is provided and, as it is drawn off the tube, transverse seals being made to form it into separate compartments which are separated to yield the individual packets. It is also known to make the transverse seals and separate the packets by traversing an ultrasonic sealing device across the flattened tubular web and back.
According to a further aspect of the present invention, the sealing and separating process is accelerated without incurring any significant additional costs by performing the cutting and sealing operation over the width of the tubular web in a single pass whereby successive packets are sealed closed and separated by displacements of the ultrasonic sealing device in opposite directions.
The sealing device can be located on a rotary mounting that pivots coaxially to the forming tube to perform successive cutting and sealing operations in mutually transverse directions, so producing tetrahedral-like packets.